Guidance device



Jan. 26, 1960 c. M. WITCHER 2,922,992

GUIDANCE DEVICE Filed larch 13, 1956 2 Shani-Sheet 2 LENS PHOTO CELLusa'r some:

h-- AREA -T mR o SOANNED H LENS . PHOTO CELL SOURCE 4o INVENTOR-CLIFFORD M. WITCHER ATTORNEY United States Patent GUIDANCE DEVICEClifford M. Wltcher, Belmont, Massi, assignor to the United States ofAmerica as represented by the Secretary of the Army Application inn-ch13, 1956, Sel'ill No. 511,357

4 Claims. 01. 340-258) This invention relates to a sensory aid devicewhich automatically signals to a user in the absence of normal vision towarn him of a sharp decline in the terrain over which he is moving. Theinvention is useful for traveling in darkness or for a blind person towarn him of the presence of a dangerous decline such as an embankment, acliff or a flight of stairs.

The complete apparatus including the necessary power supply meanstogether with the necessary optical and electrical elements aredesirably encased in a small portable housing. Its power supply may belightweight batteries of the primary type or the rechargeable type. Theapparatus is conveniently carried by a handle preferably on the topportion of the casing. A small electric lamp and a narrow beam reflectorare mounted on the casing to project radiant energy in the direction inwhich the user is moving. Means are provided to scan the beam in such amanner that it will periodically traverse a path in front of and alongthe direction of travel. Optical means are provided to intercept andfocus light reflected from a small spot on the terrain at a positionbetween the forward and back extremity of the scanned area. The point atwhich the reflected light is intercepted should be vertically separateda substantial distance from the beam of the light source. The focusedimage of this spot is directed upon a light sensitive cell whose outputis applied to the grid of an electron tube to bias the tube to cutoffwhen light from the beam is reflected to the cell. If a sharp decline inthe terrain is encountered a shadow will be cast between the spot andthe light source. When this occurs the cell is not energized and thebias on the grid of the tube is shifted to cause plate current to flow.The output of the tube is then utilized to actuate an alarm thus warningthe user of the presence of the decline.

The principles of the invention are presented herein in connection witha specific application but the invention may be embodied in otherapparatus of a similar nature defined by and within the scope of theappended claims.

It is a primary object of the invention to provide a device toautomatically energize an identifiable alarm by sense of touch orhearing thus to give warning to the user of a dangerously sharp declinein his path.

It is a further object of the invention to provide a step downindicating means wherein the signal is derived from a beam of lightfunctioning in connection with an electrooptical sensing means.

A further object of the invention is to provide indicating means of theabove indicated type which is self-powered and light in weight.

A further object of the invention is to provide a stepdown detectingmeans capable of discriminating against the operating signal and signalsoriginating from other ambient sources to radiant energy.

Other objects and features of the invention will more fully appear fromthe following description and will be particularly pointed out in theclaims.

To provide a better understanding of the invention a ice particularembodiment thereof will be described and illustrated in the accompanyingdrawings in which Fig. 1 is a side elevation of the apparatus withportions of its casing broken away.

Fig. 2 is a diagrammatic illustration showing the functionalinterrelation of certain of the components of the apparatus.

Fig. 3 is a detail schematic illustration of a combined circuitinterrupting device and beam scanning means.

Figs. 4 and 5 are diagrammatic views showing the path of the radiantenergy in the operation of the device.

Referring to the drawings, particularly to Fig. l, the completeapparatus is shown inclosed in a casing 6 which is small in size, lightin weight and readily carried by the user. The apparatus is providedwith a radiant energy beam scanning means which is situated within thecasing desirably in the lower forward portion thereof. Any suitablemeans may be used to create and scan the beam. Such a means is shownpartially diagrammatically in Fig. 3 of the drawings and comprises asmall electric lamp 7 mounted at or near the focus of a narrow beamreflector 8. The lamp and the reflector provide a beam of light 9 whichis projected forwardly and downwardly in front of and along the path ofthe person carrying the device. The lamp and reflector are mounted upona member 10 of magnetic material which constitutes the armature of anelectromagnet 12. The member 10 is supported upon a fulcrum 13 and isprovided at its end opposite the fulcrum with an insulated contactmember 14 which coacts with a second insulated contact member 15, thetwo contacts providing a circuit interrupting switch.

Since it is desired that the vibrator mechanism function at a certainfrequency such as 30 cycles per second and that the armature travel acertain distance, suitable adjustments are provided to coact with themechanical and magnetic characteristics of the device to obtain thedesired result. The chief mechanical and magnetic factors are theoperating strength of magnetic attraction of the annature to the magnet,the weight of the armature assembly, the extent of desired movement ofthe armature and the tension of the spring type fulcrum 13 or otherspring return device. The adjustments may be of any suitableconstruction such as the set screw 16 which may act in conjunction withthe contacts 14 and 15 which in turn may be bent or otherwise moved intoa desired position to obtain the desired adjustment. Other means may beemployed to scan the beam 9.

The lamp, the reflector and their support 10 together with the magnet 12are positioned to project the beam of light forwardly in the directionin which the user is moving and downwardly at the required angle tosweep the beam along the terrain for a distance of about five to sevenfeet in front of the user. The lamp 7 is provided with power from anysuitable source such as by a battery 17 the flow of power thereto beingcontrolled by a switch 18. .The battery is also connected to the contactmember 14. The circuit thru the lamp is completed thru a groundconnection. The contact 15 is connected to a coil 19 wound upon a core20 which constitutes the electromagnet 12. The other terminal of thecoil 19 is connected to ground.

When the switch 18 is closed battery current flows in the coil 19 whichmagnetizes the core 20 and attracts the armature 10 breaking the contactbetween the members 14 and 15 to open the circuit to the coil thusdemagnetizing the magnet. The tension of the fulcrum member 13 thenmoves the armature again into circuit closing position at which time thecycle is repeated. A satisfactory operating frequency has been found tobe 30 cycles per second. Any suitable frequency may be used, however.Thus while the apparatus is in use the beam is scanned along the terrainin the path of the user at the specified frequency rate and along thespecified scanning distance. Desirably, the lamp and reflector aresituated inside the lower section of the front wall 21 of the casing 6.An aperture 22 is provided to allow the passage of the light beam. I

Operation of the apparatus depends upon the detection of light reflectedfrom a small area 23 situated along the path of the user and coincidingwith the area scanned by the light source. Such detecting meansdesirably is situated within the upper portion of the casing 6 andcomprises a plane mirror preferably mounted on top of the casing at itsforward portion and disposed at an angle to reflect light from the area23 vertically downward. A lens 25 is positioned below-the mirror andserves to concentrate the light reflected from the spot 23 upon a smallphotocell 26. The power of the lens and the size of the sensitive areaof the cell determine the area of the spot 23.

For most efiicient operation in detecting step-down conditions in thetraveled terrain the separation of the light source and the point atwhich the reflected energy is received should be as large as possible.As will be apparent by reference to Fig. of the drawings the ability ofthe device to reach into the shadow area cast by the edge of thedeclining terrain is dependent upon the angle of the reflected beam withrespect to level ground. This angle should be as great as possibleotherwise the incident energy may not be cut off by the decline of thesurface or may be only partially cut ofl thus impairing the efliciencyof the device.

The manner of supplying power to the various units of the apparatus isnot to be restricted to the specific circuits and elements describedherein. A suitable means is provided for supplying the relatively highdirect current plate circuits of the electronic devices such as thephotocell, the switching tube and the amplifier tubes which are used inthe apparatus. Such high voltage may be derived partially from themagnetic beam scanning device which also provides a source of pulsatingcurrent. This pulsating current is taken from the magnet winding 19 andis fed to a transformer and rectifier unit 27 thru a connection 28. Theunit 27 contains a step-up transformer and a rectifying device togetherwith suitable current smoothing elements. The output of the unit 27 isfed to the various components as indicated diagrammatically in Fig. 2.

The photocell 26 receives its operating energy from the source 27 andsince, as will appear hereinafter, the cell receives a series ofsuccessive reflections from the scanned light beam its .output ispulsating at the frequency of each half cycle of the scanning frequencywhich in the special case described herein would be 60 cycles persecond. The output of the cell may be fed directly to an amplifier andthence to a relay to control an alarm device. It has been found,however, that for operation of the device under most conditions ofambient light such as sunlight the cell output desirably is fed to afilter 29 which freely passes the output of the cell at the operatingfrequency and discriminates against other radiant energy which may reachthe cell 26. The output of the filter is fed to an amplifier 30 theoutput of which is, in turn, rectified in the rectifier 31 and is thenfed to the grid of a switching tube 32.

So long as the photocell receives a signal the grid of the tube 32 ismaintained at cut off bias and no signal is transmitted to the user.When the signal to the cell is cut off, in a manner to be explainedhereinafter, the bias on the tube 32 shifts to a value which permits thetube to conduct and thence acting thru timing devices 33 and 34energizes the relay 35 which closes a circuit 36 leading from the coil19 of the magnetic interrupter to an alarm device 37. The device 37desirably is in the form of a solenoid having a coil 38 within which isreceived an armature 39 which in turn is mechanically coupled to acarrying handle 40 on the casing 6. Since the current flowing in thecircuit 36 in pulsating a vibration is set upinthehandleflandisfeltbytheuser.

Figs. 4 and 5 of the drawings illustrate diagrammatically the manner inwhich the device functions in use. In Fig. 4 the device is shown asbeing transported over level terrain having no step-down or sharplydeclining areas.

5 In such case the traversed light beam moves between the lines 40 in anuninterrupted path in front of the user who is traveling in thedirection of the arrow. The optical system including the mirror 24, thelens 25 and the cell 26 are so positioned that light from the spot 23approximately midway of the traverse of the beam is reflected to thecell 26 each time the beam passes the spot. Extraneous light reachingthe cell tending to produce a false signal is stopped by the filter 29.

Fig. 5 illustrates a difierent condition; namely, that which isencountered when the user approaches a decline in the terrain. In theillustration such a decline is indicated as a flight of steps. At thistime the spot 23 from which the signals originate is in the shadow ofthe step with respect to the scanning beam. The cell 26 thereforereceives no signal and the bias on the tube 32 is shifted to theconducting region resulting in actuation of the alarm to warn the user.

In the latter case the alarm timing unit 34 functions to maintain thesignal in operation until level terrain is again reached. The timingdevice may be of any suitable construction such as a conventionalinterval timer which is adjusted to open and close the relay 35 at anydesired time interval such as every .3 to .4 of a second.

If a shallow decline is encountered where the signal to the photocell isinterrupted only momentarily the timing device 33 acts to close therelay for a period of time which distinguishes from the time period ofthe timer 34.

For instance, the time period of the device 33 may be three-fourths of asecond after which the alarm shuts off.

Any suitable power supply may be used for heating the cathodes of thevarious tubes employed in the apparatus.

Such a power supply may be a low voltage battery or any suitable sourcenot shown. Suitable switches not shown are provided for controllingoperation of the device. It

0 should be understood that the specific circuit and use of the elementsas described above are presented as on example of the application of theinvention. Other arrangements and circuits may be used within the spiritand scope of the claims.

It should be pointed out that the use of the term radiant energy isintended to relate to the type of energy represented by the visible,infra-red, or ultra-violet spectrum. The special characteristics of suchenergy should be to sharply define a shadow cast by an object in itspath. Some forms of energy are not suitable since they would be onlypartially eflective in distinguishing between an irradiated areareceiving energy directly from a source, from an area immediatelyadjacent that area but screened by an intervening object which creates ashadow.

The device of the invention is highly eflicieut in detecting stepdownconditions and may readily be combined with aparatus for detecting andoutlining obstacles.

What is claimed is:

l. A portable sensory aid device comprising an electromagnetic vibratorhaving a moving armature, a radiant energy source having means toproject a narrow beam therefrom, said light source being secured to andmoving with said armature, means on said magnetic vibrator to maintain asubstantially fixed operating frequency of vibration, a pivot to guidesaid armature to swing in a plane positioned to scan the beam from saidlight source upon an elongated area in front of the user, a radiantenergy sensitive cell, means above said energy source acting to directbeam energy reflected from a selected portion of said scanned area tosaid sensitive cell, a warning alarm and electronic switching meansconnected between said cell and said alarm acting. to cut ofi said alarmwhen the cell receives reflected light from the scanned area and toactuate the alarm when no reflected signals are received.

7 2. Aportablesensoryaiddevicecomprisingacarrying case having a handle,means for projecting a beam of radiant energy upon the path in front ofthe user, automatic means to scan said beam forward and backward alongthe said path, a radiant energy sensitive cell, means a sub-.

stantial distance above said beam projecting means act ing to directbeam energy reflected from a portion of the scanned area to said cell, amagnetic solenoid, a pulsating power source, a relay operable to connectsaid solenoid with said pulsating power source, electronic switchingmeans connected between said cell and said relay operable to actuatesaid relay into closed circuit condition when said cell has no output,mechanical coupling means from the armature of said solenoid to saidhandle whereby a warning is given to the user when a decline in his pathof travel cuts off reflected signals to said cell.

3. A portable sensory aid device comprising means to project a beam ofradiant energy in front of the user, automatic means to scan said beamforward and backward along the path of the user, said scanning meanshaving a fixed scanning frequency, a radiant energy sensitive cell,means a substantial distance above said beam projecting means acting todirect beam energy reflected from a portion of said scanned area to saidcell, a frequency filter connected to the output of said cell adjustedto pass the frequency of the signals reflected from said scanned areaand reject other frequencies, a warning alarm having a source of power,a relay for controlling said alarm, connections from the output of saidfilter to the input of said relay whereby the operation of the alarm iscontrolled by radiant energy signals reaching the said cell reflectedfrom said scanned area to the exclusion of radiant energy signalsreaching the cell from other sources.

4. A portable sensory aid device comprising power supply means, meansfor projecting a beam of radiant energy energized from said powersupply, means for scanning the beam from said projecting means forwardand backward in front of the user, said scanning means having anelectromagnet, a movable armature actuated by said magnet and upon whichsaid projecting means is secured, means on said armature acting tointerrupt power supplied to said magnet during each cycle of movement ofsaid armature whereby the armature is vibrated which results in scanningsaid energy beam, a radiant energy sensitive cell, means above said beamscanning means for directing beam energy reflected, from a portion ofthe scanned area to said cell, an amplifier connected to the output ofsaid cell, a warning alarm, a relay connected to the output of saidamplifier, a circuit from the coil on said electromagnet thru said alarmand to the control contacts of said relay whereby pulsing current tosaid alarm is controlled by the output of said cell, a high voltagedirect current source having a step-up transformer and rectifier,connection from the magnet of said electromagnetic scanning means to theprimary of said transformer and connections from the output of said highvoltage source to the elements of the apparatus requiring such voltage.

References Cited in the file of this patent UNITED STATES PATENTS2,060,200 Hammond Nov. 10, 1936 2,600,708 Ulrich June 17, 1952 2,639,418Sundstrom et al May 19, 1953 OTHER REFERENCES Article on pages 116-119of the March 1946, issue of Electronics, entitled Sensory Aid for theBlind.

Article on page 168 of the September 1955 issue of Electronic Design,entitled Light Location for the Blind."

